The popular debate about the ancient Indus script and whether it constitutes a language system seems to continue with strong arguments and interesting examples:
Reply to Rao et al. and Lee et al. by Richard Sproat.
I think unless we settle on a definitive set of statistical tests that can tell if a given set of sequence is taken from a language we’ll see more of this debate. Whether such a set of tests can exist is a very interesting question by itself!